There has been proposed a voltage supply device such that an airflow generation device using plasma is disposed on the surface of a rotation blade included in a rotation apparatus such as a fan, a windmill or a turbine, and a voltage is supplied to a rotation field. This voltage application device applies a voltage between a first electrode of the airflow generation device provided on the surface of the blade which rotates and a second electrode disposed separately from the first electrode, to thereby generate airflow between the first electrode and the second electrode. Thus, there is exerted an influence on the velocity distribution of a boundary layer on the surface of the rotation blade, and separation is suppressed and variation in flow velocity is reduced, thereby stabilizing the airflow, reducing noise and vibrations, and improving aerodynamic properties of the blade.
However, it has been found that there is a possibility of electromagnetic noise to be mixed in the airflow generation device. For example, when a high-frequency high voltage is transmitted via a sliding type transmission unit electrically connecting a rotation side and a fixed side of the rotation apparatus, a sliding part of the sliding type transmission unit varies irregularly in contact surface area and contact resistance due to irregularities of the sliding part and unevenness in pressing forces. Accordingly, small discharge occurs in the vicinity of the sliding part corresponding to this variation, and electromagnetic noise due to the discharge occurs. Thus, not only the influence of noise on other devices in the periphery arises, but also the electromagnetic noise mixes into power supplied to the airflow generation device. This causes operation of the airflow generation device to be unstable, and the effects such as reduction in noise and vibrations as well as efficiency improvement cannot be obtained sufficiently. Further, the transmission unit wears out due to the discharge in the sliding type transmission unit, which becomes a factor of increasing running costs.